首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   832篇
  免费   66篇
  2023年   4篇
  2022年   7篇
  2021年   25篇
  2020年   14篇
  2019年   22篇
  2018年   30篇
  2017年   25篇
  2016年   23篇
  2015年   35篇
  2014年   44篇
  2013年   40篇
  2012年   51篇
  2011年   45篇
  2010年   45篇
  2009年   32篇
  2008年   54篇
  2007年   43篇
  2006年   41篇
  2005年   51篇
  2004年   42篇
  2003年   20篇
  2002年   30篇
  2001年   25篇
  2000年   9篇
  1999年   17篇
  1998年   7篇
  1997年   8篇
  1996年   3篇
  1995年   2篇
  1994年   6篇
  1993年   4篇
  1992年   11篇
  1991年   5篇
  1990年   3篇
  1989年   6篇
  1988年   7篇
  1987年   3篇
  1986年   4篇
  1985年   2篇
  1984年   9篇
  1983年   8篇
  1981年   4篇
  1980年   5篇
  1979年   4篇
  1978年   3篇
  1976年   2篇
  1973年   5篇
  1972年   2篇
  1971年   3篇
  1970年   2篇
排序方式: 共有898条查询结果,搜索用时 203 毫秒
111.
The GLIS family zinc finger 3 isoform (GLIS3) is a risk gene for Type 1 and Type 2 diabetes, glaucoma and Alzheimer's disease endophenotype. We identified GLIS3 binding sites in insulin secreting cells (INS1) (FDR q < 0.05; enrichment range 1.40–9.11 fold) sharing the motif wrGTTCCCArTAGs, which were enriched in genes involved in neuronal function and autophagy and in risk genes for metabolic and neuro-behavioural diseases. We confirmed experimentally Glis3-mediated regulation of the expression of genes involved in autophagy and neuron function in INS1 and neuronal PC12 cells. Naturally-occurring coding polymorphisms in Glis3 in the Goto-Kakizaki rat model of type 2 diabetes were associated with increased insulin production in vitro and in vivo, suggestive alteration of autophagy in PC12 and INS1 and abnormal neurogenesis in hippocampus neurons. Our results support biological pleiotropy of GLIS3 in pathologies affecting β-cells and neurons and underline the existence of trans?nosology pathways in diabetes and its co-morbidities.  相似文献   
112.
We previously described an enrichment-immunoassay utilizing a T6 monoclonal antibody capture enzyme-linked immunosorbent assay. Here we evaluated it for the rapid screening for Salmonella in fishmeal obtained from the national Animal and Plant Quarantine service in the People's Republic of China. In this method, the number of Salmonella present is first expanded by appropriate enrichment cultures, and the pathogens are then directly detected by the T6 immunoassay. In a total of 94 enrichment cultures of fishmeal, we obtained an overall concordance of 98% between the results obtained in parallel by this method and by conventional test method. The positive prediction by this method was 92% and the negative prediction was 100%. The turn around time for the new test was 27 h which is a significant improvement from the turn around time exceeding 96 h required for the conventional test method. This test proved to be compatible with the routine work flow in the practical setting of a quarantine laboratory.  相似文献   
113.
G protein-coupled receptors are usually thought to act as monomer receptors that bind ligand and then interact with G proteins to initiate signal transduction. In this study we report an intracellular peripheral membrane protein named the calcitonin gene-related peptide (CGRP)-receptor component protein (RCP) required for signal transduction at the G protein-coupled receptor for adrenomedullin. Cell lines were made that expressed an antisense construct of the RCP cDNA, and in these cells diminished RCP expression correlated with loss of adrenomedullin signal transduction. In contrast, loss of RCP did not diminish receptor density or affinity, therefore RCP does not appear to act as a chaperone protein. Instead, RCP represents a novel class of protein required to couple the adrenomedullin receptor to the cellular signal transduction pathway. A candidate adrenomedullin receptor named the calcitonin receptor-like receptor (CRLR) has been described, which forms high affinity adrenomedullin receptors when co-expressed with the accessory protein receptor-activity modifying protein 2 (RAMP2). RCP co-immunoprecipitated with CRLR and RAMP2, indicating that a functional adrenomedullin receptor is composed of at least three proteins: the ligand binding protein (CRLR), an accessory protein (RAMP2), and a coupling protein for signal transduction (RCP).  相似文献   
114.
Chemical analysis of pheromone gland extracts followed by behavioural studies in the wind tunnel and by field trapping tests show that the sex pheromone of the Guatemalan potato moth, Tecia (Scrobipalpopsis) solanivora Povolny (Lepidoptera: Gelechiidae), is a blend of (E)‐3‐dodecenyl acetate, (Z)‐3‐dodecenyl acetate, and dodecyl acetate. A 100 : 1 : 20 blend of these compounds, formulated at 1000 µg on rubber septa, captured more males than the main compound alone. This lure was species‐specific and did not capture the potato tubermoth, Phthorimaea operculella. A potato field was treated with a blend of these three compounds at a rate of 28 g ha?1. Male T. solanivora attraction to synthetic pheromone traps was almost completely suppressed for 2 months, demonstrating the potential use of pheromones for control of this economically important insect pest of potato in Central and Southern America.  相似文献   
115.
116.
The largest semi-enclosed basin in the world, the Mediterranean Sea, is characterized by high biodiversity and heavy human pressure on the coastal system. The Strait of Sicily (SoS) represents the boundary between western and eastern Mediterranean sub-regions and is an important biodiversity hot spot. Given its ecotonal nature and it being a “crossroad” for the westward expansion of warm-temperate and tropical species from the Levantin basin, the SoS is likely to play a key role in future climate change related biodiversity changes within the Mediterranean. The complexity of the SoS ecosystem, characterized by wider shallow detritic and rocky banks on the continental shelf hosting large biodiverse communities, and peculiar circulation pattern, promotes species diversity and abundance. In addition, the deep-sea is characterized by the occurrence of extremely vulnerable habitats, such as deep-water communities of scleractinian corals, antipatharians, gorgonians, and red coral. We review the current knowledge on the main characteristics of the north sector of the SoS ecosystem. The SoS ecosystem is increasingly threatened by expanding anthropogenic pressures in the area and specific conservation measures should be implemented on a national and international level to protect the relevant and vulnerable habitats.  相似文献   
117.
Genetic diversity and structure of Pseudoplatystoma corruscans and P. reticulatum, large migratory South America catfishes, where overfishing and the construction of numerous dams in their feeding and reproducing areas are affecting their migratory processes negatively, were studied using microsatellites in samples from Paraguay (that comprises the Pantanal biome), and the upper and lower Paraná Basins. Genetic diversity was in accordance to that observed for other large migratory fishes, but the most geographically isolated populations of P. reticulatum and those P. corruscans subject to anthropogenic effects (stocking and dams) showed lower genetic diversity and evidences of bottlenecks compatible with low effective population size. Pseudoplatystoma reticulatum presented subtle genetic differentiation within the Paraguay area, especially between the edges of its distribution. Pseudoplatystoma corruscans, in this same area, presented a quite homogeneous but significant genetic break between the Paraguay and upper Paraná populations, apparently resulting from natural and historical isolation between the basins until recently. These data demonstrates that, although these Pseudoplatystoma spp. are abundant in the Pantanal area, anthropogenic events are leading to negative effects on their populations, particularly in the upper Paraná Basin. Genetic differentiation observed along each species distribution demands conservation actions to preserve each population's biodiversity. These results represent important genetic information using new microsatellite markers and the first genetic study of P. reticulatum covering this area of its native distribution. Data may also contribute to a better understanding of species migration patterns and to be used as a baseline for proper management.  相似文献   
118.
119.
The aim of the present study is to analyze the morphologic changes occurring along the period of a woman's life thatareknown as climacterium. Our sample consists of 648 women from different provinces of Cuba, but who lived in Havana for at least 15 years. Morphological variables such as height, weight, biliocristal and biachromial diameters and six subcutaneous fat skinfolds were measured. With regard to the menopausic condition, the sample was divided into three subpopulations: premenopausic, naturally menopausic and surgically menopausic (when the two ovaries had been removed). Age at menopause was calculated by both the “retrospective” (49.45±0.49) and “status quo” (48.83±0.02) methods. The results obtained point towards morphological differences between pre- and postmenopausic women. We observed greater accumulations of fatty tissue in the suprailiac regions of postmenopausal females. Lean body mass represents a bigger fraction of the total body weight in women who are still menstruating. In the case of surgically menopausic women, they are at a mid-distance between the premenopausic and naturally menopausic subpopulations. A discriminant analysis was carried out which confirmed the results previously observed. From this analysis it appeared the body mass index and the subcutaneous skinfolds are the variables that discriminante, that is, separate, the three subsamples.  相似文献   
120.

Background  

Mannose binding lectin (MBL) is an important host defence protein against opportunistic fungal pathogens. This carbohydrate-binding protein, an opsonin and lectin pathway activator, binds through multiple lectin domains to the repeating sugar arrays displayed on the surface of a wide range of clinically relevant microbial species. We investigated the contribution of MBL to antifungal innate immunity towards C. parapsilosis in vitro.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号